Heat Transfer

251. It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is

1. 3.06 × 10⁵
2. 6.12 × 10⁵
3. 7.24 × 10⁵
4. 9.08 × 10⁵

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252. It is not preferable to use superheated steam in evaporators, because of its very

1. High temperature
2. High pressure
3. Low film co-efficient
4. None of these

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253. It is not recommended to use a 1-2 shell and tube heat exchanger for a particular heat duty, whenever the LMTD correction factor is

1. > 0.75
2. < 0.75
3. < 0.50
4. < 0.25

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254. jH factor for heat transfer depends upon the _________ number.

1. Biot
2. Nusselt
3. Reynolds
4. Prandtl

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255. jH factor for heat transfer is not a function of the _________ number.

1. Reynolds
2. Nusselt
3. Grashoff
4. Both (B) & (C)

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256. Kg of liquid evaporated per hour in an evaporator is defined as its

1. Capacity
2. Economy
3. Steam load
4. None of these

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257. Kirchoff's law is applicable to

1. Monochromatic radiation only
2. Total radiation only
3. Both (A) and (B)
4. Only volumes and not to surfaces

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258. Kirchoff‟s law applies to _________ radiation.

1. Total
2. Monochromatic
3. Both (A) & (B)
4. Neither (A) nor (B)

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259. Latent heat absorbed by 1 lb of water at 212°F, when it is changed to steam at 212°F, may be around _________ BTU.

1. 180
2. 970
3. 3.97
4. None of these

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260. Leidenfrost point is a term concerned with the

1. Condensation of the saturated vapor on a cold surface
2. Concentration of a corrosive solution by evaporation
3. Heat transfer between two highly viscous liquids
4. Boiling of a liquid on a hot surface

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